Molecular tectonics: crystal engineering of mixed valence Fe(II)/Fe(III) solid solutions

Area of Science:

• Materials Science
• Inorganic Chemistry
• Crystallography

Background:

• Isostructurality is key to forming solid solutions.
• Mixed-valence compounds contain ions in multiple oxidation states.
• Cyanide-based coordination polymers offer diverse structural possibilities.

Purpose of the Study:

• To synthesize and characterize a novel mixed-valence iron cyanide solid solution.
• To investigate the formation of unique composite crystal structures.
• To explore the relationship between isostructurality and crystal formation.

Main Methods:

• Crystallization by combining a dicationic tecton (2) with cesium iron(III) hexacyanidoferrate(III) (M(3)Fe(III)(CN)6) and cesium iron(II) hexacyanidoferrate(II) (M(4)Fe(II)(CN)6).
• X-ray diffraction analysis to confirm isostructurality and determine crystal structures.
• Spectroscopic methods to confirm the mixed-valence state of iron.

Main Results:

• A rare hydrogen-bonded mixed-valence iron(II)-iron(III) solid solution was successfully generated.
• The solid solution exhibits a specific composition: ((Cs(2)2(3)-[Fe(II)(CN)6](2))(0.83)(2(3)-[Fe(III)(CN)6](2))(0.17)).
• Curious necklace-like composite crystals were also formed, indicating complex crystal growth phenomena.

Conclusions:

• Isostructurality between related iron cyanide frameworks facilitates the formation of mixed-valence solid solutions.
• The study demonstrates a novel method for creating mixed-valence iron cyanide materials with interesting structural motifs.
• The findings contribute to the understanding of crystal engineering and the design of functional inorganic materials.